The invention relates to a synchronization device.
Multi-step gear wheel transmissions are at present being practically exclusively used for transmitting the input power and adapting the motor torque to the traction requirement of a vehicle.
The shift system of the transmission can be considerably simplified with the aid of a synchronization device. In the synchronization, the rotational speed adaptation of the transmission components to be interconnected is carried out automatically or controlled in order to prevent double declutching during upshifts or double declutching with high switching of the throttle during downshifts. The traveling safety is clearly improved since the change of gears is quickly, safely and also noiselessly possible even under critical driving situations, e.g. when driving downhill the driver""s right foot can remain on the brake during a downshift.
A synchronization system has the following tasks to perform:
rotational speed adaptation of two transmission components and the parts connected therewith that rotate at different speeds so that they can be interconnected with positive fit without grating noise;
locking of the positive-fit connection until synchronous speed of the transmission components to be connected is reached in order to prevent grating and damages of the positive-fit shifting components;
release of the lock at the moment of synchronous speed;
rotational speed adaptation within the shortest time and with the least possible shifting forces;
operational safety even under unfavorable circumstances such as in case of cold, viscous oil or of extremely quick breaking of the gears.
In the synchronized vehicle transmissions existing at present, synchronization devices for each separate gear are mostly used.
Lock synchronization with cones has been broadly extended at the same time. In this system, friction cones are used for the force-locking rotational speed adaptation of the transmission components to be connected. This kind of synchronization is used in the transmissions both of passenger cars and of industrial vehicles.
The customary synchronization devices make the three basic functions of the synchronization available:
often arbitrary lockable and releasable connection of two parts rotating around a common axis;
energy transmission to or energy drawing from a rotary part (acceleration, deceleration); and
adjustment of the rotational speed difference between two parts rotating around a common axis to a value equal to or near zero.
In synchronization systems with friction disks, the conical friction members are replaced by a number of disks which rub against each other during rotational speed compensation. In one version, disks axially abutting on each other in a sequence are connected with the synchronizer ring or the transmission shaft or, on the other hand, with the clutch body on the gear wheel or with the gear wheel itself. Such a synchronization system which, e.g. can also be equipped with a reinforcer device of the synchronizing force, has been disclosed in DE 32 08 945 A1.
From DE 195 06 987 A1 is known as a generic form fit gear clutch, the synchronizer sleeve of which is formed by an outer driver ring in which a shift fork engages, and by a shift hub which is non-rotatably but axially movably situated upon a synchronizer body. The shift hub carries selector teeth which interact with a dog clutch on a clutch body. The front faces of the selector teeth and the dog clutch are in corresponding revolution surfaces so that they bluntly strike on each other under axial shift movement. The clutch body is non-turnably but axially, elastically and flexibly connected with a gear wheel rotatably supported upon a transmission shaft.
Between the synchronizer body, non-rotatably connected with the transmission shaft, and the driver ring, is situated a slipping clutch in the form of a spring-loaded, lined multi-disk clutch, the driver ring being designed as an outer disk carrier and the shift hub as an inner disk carrier. On the front side of the shift, hub lids are mounted which, with radial play, extend toward the driver ring and between which the lined disks support themselves under the pressure of a corrugated spring.
The outer periphery of the driver ring carries a meshing gear which interacts with driver teeth of a driver which is connected with the gear wheel non-rotatably, but axially and elastically flexible. The teeth of the driver are narrower than the tooth gaps so that in the peripheral direction an abundant play is formed which facilitates meshing of the meshing gear during shifting. The front faces of the driver teeth and of the meshing gear are in a conical revolution surface so as to form an angle in the axial direction toward the peripheral surface and toward the front face of the driver.
If the synchronizer sleeve is moved from its neutral position in the shifting position direction, the meshing gear of the driver ring first comes into contact and engagement with the teeth of the driver so that a slipping torque is transmitted, via the lined disks, from the gear wheel to the transmission shaft. The torque depends on the number of disks, the radius of the disks and the force of the corrugated spring. The necessary time in order to produce the synchronous speed between the gear wheel and the transmission shaft is decisive. Locking surfaces on the driver teeth prevent the shift teeth of the hub part coming into contact with the dog clutch before an approximately synchronous speed has been reached between the gear wheel and the transmission shaft.
It is obtained through the front faces extending into the revolution surface of the driver teeth, of the meshing gear, of the dog clutch, and of the selector teeth, that torques produced by the transmission components to be coupled exert no reaction forces on the shifting force. In addition, due to the axial flexibility of the driver and of the clutch body, contact impacts on the driver teeth and dog clutch are softly trapped thus over the whole shift stroke, a relatively uniform shifting force results which improves operating comfort.
Internal disks are customarily coated on both sides while the outer disks are uncoated steel disks, but disks coated on one side can also be used.
Disk synchronization, according to the prior art, has the disadvantage that in the range of the meshing gear, wear can be found which is generated due to the impingement of the tooth front edges and front surfaces during full differential rotational speed.
The problem on which the invention is based is to reduce the wear in the area of the meshing gear.
The height of the meshing pulse directly depends on the friction torque of the disks. The lower the friction torque of the disks, the smaller is the pulse and the wear. It is proposed, according to the invention, to provide on the synchronization system means which, upon engagement, divide the torque transmitted among the teeth of the synchronizer sleeve and the teeth on the clutch body into an initial lower meshing torque and a subsequent larger synchronizing torque.
In an advantageous design, the means are formed by grading of the disks enabling a successive engagement of the disks of the synchronization system in the torque transmission.
Another advantageous embodiment shows the grading of the disks in a manner such that at least one first step is provided to form the meshing torque and at least one second step to form the synchronizer torque.
Another advantageous design on the first step has two friction surfaces to form the small meshing torque and on the second step ten friction surfaces to form the synchronizer torque.
In another advantageous embodiment, the step between the engagement of two successive disks is formed so that the shifting vibrations are reduced.
When the teeth move on the synchronizer sleeve in the direction of the teeth on the clutch body of a transmission part to be engaged, in the first step, the driver teeth of the disks grips only the edge of the synchronizer sleeve first, with at least one disk, in order to produce with the disk and appertaining friction surfaces a friction torque corresponding to a meshing torque. The build up of the meshing torque is earlier than the build up of the synchronizer torque proper, which should cause the approximation of rotational speed. Due to the prior meshing torque, the engaging torque stops are kept out of the synchronization system which would result if from the start the synchronization operation were begun with the full friction torque of all disks. Thus a practically easy pre-synchronization takes place followed by the real synchronization.